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Description

Copyright 2001

Dimensions: 7-3/8x9-1/4

Pages: 624

Edition: 1st

Book

ISBN-10: 0-201-72827-3

ISBN-13: 978-0-201-72827-9

PacketCable promises to be one of the most important developments in networking technology to date. The PacketCable network, a project managed by the Cable Television Laboratories consortium, is expected to be deployed by all major American cable companies as well as many overseas cable operators. The large-scale PacketCable network enables high-speed simultaneous transmission of digital computer data and telephone voice signals over cable modems and facilitates the widespread deployment of video and voice Internet applications, such as video conferencing, by utilizing cables that are already in place through cable T.V. Developed through the cooperative efforts of numerous cable television operators and telephony and networking vendors, the specifications enable cable modems to compete aggressively with twisted-pair telephony and DSL technology.

Written for anyone with a stake in this up-and-coming field, Digital Telephony Over Cable serves as a companion guide for implementors and managers alike. It provides an accessible overview of more than a thousand pages of technical specifications with in-depth explanations of the most salient features, and offers extensive background on many of the underlying technologies that make digital telephony over cable possible. You will learn how all of these specifications come together to create a complete, functional telephony network running over a shared access medium.

Preface

We live in interesting times, especially in the telecommunications industry. The ubiquity of cellphones, deregulation, voice mail (a double-edged sword if ever there was one), cheap long-distance phone service, direct international dialing, broadband access, always-on access to the Internet--the list of recent fundamental changes in the way that telecommunications impact ordinary consumers could probably extend over several paragraphs. Despite the many changes that have occurred, there seems no reason to believe that the flood of new services will not continue for at least the next half decade, and probably longer.

This book describes a brand new communications technology that is in the process of moving from small-scale trials to full national deployment.

Starting in the late 1990s, consumers have become acquainted with the notion of broadband access to the Internet. The two principal methods used to provide this high-speed access are cable modems, which send their traffic through the same cable as is used to supply cable television, and variants of a technology known as DSL (Digital Subscriber Line), which works over ordinary telephone lines.

The cable and telephone companies are in a race to provide the dominant technology (either cable modem or DSL, respectively) that will provide broadband Internet access to homes. Especially in the United States, cable modem technology has maintained an early lead over DSL, in part because most cable modems use standardized technology whereas DSL technology has (so far) been hampered by the lack of a single, pervasive standard.

DSL does have one tremendous advantage, though. A DSL line can be used simultaneously to provide broadband Internet access and to place (and receive) ordinary phone calls. Until now, cable modems have provided only the first of these features. This book addresses the mechanism by which the cable companies have chosen to provide true digital telephony over the cable access network using ordinary cable modems.

The technology is known generically as Packet Cable Telephony. The particular implementation that we discuss is the result of several years of cooperative effort by cable television operators and vendors of networking and telephony equipment. Known as PacketCable™, all of the major cable companies have stated that they intend to deploy large-scale PacketCable networks in the course of the next few years.

In this book, we provide a detailed explanation of how PacketCable works. The author's intention is to provide a "one-stop" book on PacketCable for graduate students, implementers, managers and anyone else interested in understanding how a complete, functional telephony network can be built from scratch using IP (Internet Protocol) technology running over a shared access medium. This (unfortunately for the author) is a nontrivial task.

The PacketCable specifications alone run close to a thousand pages. The specifications for other technologies that are required in the network (such as the various Internet Protocol standards and the cable modem DOCSIS standards) are roughly the same length. The problem then is obvious: How can one summarize a couple of thousand pages of dense, technical documentation in a way that is simultaneously accurate, thorough and comprehensible? Clearly, something has to give.

The author has attempted to explain in some detail each of the important parts of the technology. Individual chapters are dedicated to the various principles on which PacketCable is built. The intention is that a reader with little background in either networking or telephony should be able to read a chapter--possibly in conjunction with Chapter 1 or Chapter 2--and come away with a solid understanding of exactly how PacketCable handles the particular issues discussed in that chapter.

What we do not discuss are many of the extreme cases, exceptions and detailed requirements placed on equipment by the specifications. The specifications expend a lot of effort ensuring that PacketCable equipment manufactured by vendor A is guaranteed to interoperate correctly with similar equipment manufactured by vendor B. And, in a few cases (although as infrequently as possible), we simply punt: If a feature is particularly complicated and not sufficiently central to the basic theme of explaining PacketCable, we sometimes either avoid it completely or mention it and refer the reader directly to the specifications. Usually only an implementor would be interested in such details, and an implementor should be reading the original specifications in conjunction with this book anyway.

Which brings us to the subject of the market for this book. We just mentioned three likely markets: graduate students, managers and implementors.

We anticipate that graduates working in the fields of advanced networking and telecommunications will find here a thorough explanation of the many issues (and the chosen solutions) facing anyone wishing to design a large-scale, commercially deployable digital telephony network using modern technology and protocols. Managers in the telecommunications industry will find the book useful because it encompasses the entire network. Managers need to understand the "big picture," which is provided in the first couple of chapters of the book, as well as the beginning portions of each of the remaining chapters.

For the implementor, this book is intended to provide an in-depth contextual reference for the PacketCable and other specifications. Implementors are usually concerned with the "small picture," and often this is at the expense of a good understanding of the context in which the implementor is working. Before plunging into the details of one or other of the specifications, this book is useful for providing an explanation of the specifications in ordinary words (well, mostly ordinary words), as well as providing a picture of how all the specifications fit together to define a functioning network.

I recommend reading Chapter 1 even if you have acquired this book for some of the technical material in one of the later chapters. Chapter 1 provides, among other things, an overview of the PacketCable architecture and an introduction to most of the common PacketCable devices. Also, if when skipping around you come across a term that you do not recognize, don't forget that there's a comprehensive glossary in Appendix A.

The organization of most of the chapters follows a model in which detailed information about the format of messages is provided before the higher-level picture that shows how the messages fit together to perform a useful purpose. Although this is an order of presentation that this author prefers, some people may feel uncomfortable with this approach and may prefer to skip forward to obtain a good grasp of the message flows before returning to understand exactly what is in the various messages. Feel free to skip around: It's your book, and you're entitled to use it in whatever way works for you.

The author would like to express his thanks to all who helped this book come to fruition. The author had the pleasure of working with many intelligent and knowledgeable technical architects in various PacketCable Focus Teams. Any list would be bound to miss someone, so I simply say a big "Thank you" to all.

A few people responded to specific questions while the book was being written. I would particularly like to thank Bill Marshall of AT&T Research and Flemming Andreasen, orginally of Telcordia and now with Cisco Systems, both of whom have probably forgotten more about PacketCable than any other person will ever know. Bill Kostka of CableLabs responded promptly and effectively to my DOCSIS questions, and Sasha Medvinsky of General Instruments (now Motorola) clarified several issues related to security.

CableLabs supplies liaison members to the PacketCable Focus Teams, and I would like to explicitly thank those people who fulfilled that role on the teams of which I was a member in the period that the PacketCable 1.0 specifications were being written: Ed Miller (Distributed Call Signaling), Andrew Sundelin (Dynamic Quality of Service), Glenn Russell (Dynamic Quality of Service), Chet Birger (Security), Jean Chess (Security) and Nancy Davoust (PacketCable Electronic Surveillance Protocol).

Thank you to Lucent Cable Communications in general and Jane Gambill, Marty Glapa and Rich Gitlin in particular for allowing me to represent Lucent at CableLabs. Thank you also to SecureCable, Inc. for allowing me the time to complete this book while representing them on PacketCable 1.x Focus Teams.

I wish to thank the various people at Addison-Wesley who helped make this book possible. The technical reviewers were Paul Obeda, Neil Olsen, Khaled Amer, Andrew Valentine, Don Stanwyck, Al Vonkeman, Laura Knapp, Dan Pitt and John J. Brassil. To them go my thanks for pointing out many places where the original text left something to be desired (including, sometimes, accuracy). Special thanks go to my editor, Stephane Thomas, for being such a pleasant person to communicate with on the phone and via e-mail. Thanks also to the people behind the scenes at the production department who had a hand in turning this from a word-processed document into a real book.

Thank you especially to the cable companies for seeing the need for, and supporting, PacketCable.

And, finally, a few words of blatant self-promotion. Writing a technical book is interesting, but hardly fun. One day I hope to escape the hurly-burly of real life and "retire" to write novels full-time instead of merely as time allows. In the Bad Old Days of last year, getting a novel published was much harder than publishing a technical book. After many "very-nearly-almost" acceptances by big New York publishers, I became disenchanted with the whole idea of spending several months writing a novel only to discover that every publisher had a different reason for rejecting it.

With the advent of Print-On-Demand technology, which allows publishers to print books one at a time as orders come in, my novels are now being made available. Please check out http://www.sff.net/people/N7DR/drevans.htp for details.